Method of producing magnetic alloys



Patented July 19, 1932 UNITED STATES VEBE B. BROWNE, OF BRACKENRIZDGE,PENNSYLVANIA METHOD OF PRODUCING ILAGNETIC ALLOYS No Drawing.

This invention relates to a method of manufacturing silicon steel foruse as a magnetic alloy.

Silicon steel is now largely used as a magnetic alloy in the manu actureof certain parts of electrical apparatus on account of its high degreeof magnetic permeabilit and low degree of magnetic hysteresis, and t isinvention has particularly to do with the manul0 facture of siliconsteel for use as a magnetic alloy.

An object of the invention is to produce a silicon steel alloy having ahigher degree of magnetic permeability than such alloys at present knownand used for this purpose.

A further object of the invention is to provide a silicon steel alloyfor use as a magnetic material in electrical apparatus having a lowcarbon content, andthat will be praczo ticably free from dissolvedgases.

A. further object of the invention is to provide a method by whichsilicon steel alloys having a high degree of magnetic permeability, andwhich are free from dissolved gases, may be manufactured.

Other objects of the invention will be apparent to those skilled in theart.

Silicon steel, (also known as silicon iron) has been known for some timeas a valuable iron alloy for use in electrical apparatus. Its

value is not only determined b its silicon content, but by its soundnessan purity as well. Recent research on these alloys has shown that carbonplays an important part in the value of such material, and it has nowbeen found that the presence ofdissolved or occluded gases also" playsan important part in the value of the alloys for use in the magneticcircuits of electrical apparatus.

Small laboratory quantities of silicon steel having an extremely lowcarbon content have been produced in a vacuum furnace, but by methodswhich are wholly impracticable for commercial production on a largescale.

In my prior United States patents, Numbers 1,570,229, dated January 19,1926, and. 1,574,550, dated February 23, 1926, are disclosed methods ofproducing silicon steel alloys for use in electrical apparatus. In eachof these patents the final operation is.

Application filed February 20, 1930. Serial No. 430,140.

the tapping of the low carbon iron in the molten condition into a ladlecontaining ferro silicon suflicient to bringthe alloy up to the desiredcomposition. When the iron is raised.

to a high temperature asdescrib'ed in said patents, especially whencurrents of air are passed through the metal, the melted iron dissolvesa large volume of gases. When silicon is added to the molten iron, ithas been found that the silicon increases the soluo0 bility of the ironfor the gases contained therein, with the result that all of the gaseswhich were originally held in solution on account of the hightemperature of the metal ,are retained in the final product. The gasesblown through the molten metal, and other gases Which may have beenabsorbed in the process of making the iron, include some carbon monoxideand carbon dioxide, with the result that the final product will show agreater carbon content than exists therein in the form of iron carbide;in addition to the above gases, other gases such as nitrogen andhydrogen are frequently present. The presence of the dissolved gases isdisadvantageous in this type of alloy, since it has been found that theyproduce a detrimental effect on the magnetic properties of the finalprod-' uct.

In the present invention, the product of the Bessemer, or open hearth,or electric furnace, as described in the above patents, which product isan iron free from silicon, and having a carbon content of not over 0.03percent, is subdivided by casting into suitable sized ingots which arepermitted to solidify so that the gases which are dissolved or oceludedtherein are allowed to escape during the solidification and the loweringof their temperature to the atmospheric temperature. The cooled ingots,which are now free from the dissolved or occluded gases, may then berolled and out up into suitable sizes 'for final charging into an electric induction furnace;

or instead of casting themetal into ingots, it may be cast into smallmoulds to make slabs of a suitable size for charging into the inductionfurnace direct, or the melted metal may be shotted by being cooledrapidly in water. The solid metal is then charged into the inductionfurnace and melted, with the necessary ferro silicon or other source ofsilicon to produce a desired composition in the final product, or theferro silicon or the like may be added after the iron is melted. Bythese methods I am able to produce a silicon steel alloy having a carboncontent of less than 0.03 percent, and containing the desired quantityof silicon, and which is substantially free from dissolved gases.

The silicon steel alloy produced by the methods described herein, maynow be manufactured into suitable sheets for transformer cores, or castinto suitably shaped magnetic frames; the alloy has a higher degree ofmagnetic permeability, and a lower mag-- netic hysteresis loss, than isfound in silicon steel alloys heretofore produced.

I claim:

1. A method of producing magnetic alloys including suitably producing amolten body of low carbon iron substantially silicon-free, casting thesame into suitable ingots, whereby the molten body solidifies and iscooled to atmospheric conditions, thereby expelling gases therefrom,rolling said ingots, further subdividing them, and remelting the samewhile simultaneously adjusting the silicon content to the desired amountby suitable additions to the remelted mass.

2. A method of producing magnetic silicon alloys of high magneticpermeability ineluding preparing a molten body of low carbon iron whichis substantially silicon free and which contains not over about 0.03%carbon, subdividing the molten mass into smaller parts, cooling andsolidifying the subdivided parts to about atmospheric con- :ditionsuntil they expel their gases therefrom and remelting the same Whileadjusting the silicon content by predetermined additions to the remeltedmass.

In testimony whereof I have hereunto subscribed my name this lith day ofFebruary,

VE'RE B. BROWNE.

